The invention relates to a process for converting non-aromatic hydrocarbons in the presence of a zeolite material to aromatic hydrocarbons. More particularly, the invention relates to the reduction in the rate of coke formation during the aromatization of hydrocarbons in the presence of a zeolite material to thereby enhance the stability of such zeolite material.
It is known to catalytically crack non-aromatic gasoline boiling range hydrocarbons to lower olefins (such as ethylene and propylene) and aromatic hydrocarbons (such as benzene, toluene, and xylenes) in the presence of catalysts which contain a zeolite (such as ZSM-5), as is described in an article by N.Y. Chen et al in Industrial & Engineering Chemistry Process Design and Development, Volume 25, 1986, pages 151-155. The reaction product of this catalytic cracking process contains a multitude of hydrocarbons: unconverted C.sub.5 +alkanes, lower alkanes (methane, ethane, propane), lower alkenes (ethylene and propylene), C.sub.6 -C.sub.8 aromatic hydrocarbons (benzene, toluene, xylenes, and ethylbenzene), and C.sub.9 +aromatic hydrocarbons.
One concern with the use of zeolite catalysts in the conversion of hydrocarbons in the gasoline boiling range to aromatic hydrocarbons and lower olefins is the excessive production of coke during the conversion reaction. Coke formed during the zeolite catalyzed aromatization of hydrocarbons tends to deposit upon the surface of the zeolite thereby causing deactivation. It is desirable to improve the process for the aromatization of hydrocarbons by minimizing the amount of coke formed during such aromatization reaction process.